肠道菌群代谢产物辣椒素酯通过菌群稳态/巨噬细胞极化/IL-33轴改善肠缺血再灌注损伤的作用及机制研究

Intestinal ischemia/reperfusion injury is common in perioperative period with high mortality. The mechanism of its occurrence is not yet clear, and there is no effective prevention and treatment strategy. The applicant discovered the expression of gut microbial metabolites capsiate was relatively reduced in the intestinal tract after intestinal I/R through metabolomics analysis in the early stage. Pretreatment with capsiate can improve the intestinal I/R-induced enteric dysbiosis and intestinal mucosal barrier damage. It is known that enteric dysbiosis can induce macrophages M1/M2 polarization. In addition, intestinal macrophages are an important source of cells for IL-33. Applicants' previous results found that capsiate can promote the expression of IL-33, and it is also confirmed that IL-33 can effectively improve intestinal I/R injury. Therefore, the applicant speculated that capsiate could restore intestinal barrier repair by inhibiting enteric dysbiosis after I/R and inducing the transformation of macrophages M1 to M2 and promoting the release of IL-33. In this project, macrophage knockout and IL-33 gene knockout mice were used to establish in vivo models of intestinal I/R injury, as well as antibiotics and FMT experiments to study the role and mechanism of capsiate in intestinal I/R injury. The use of microbial metabolites as a therapeutic target provides a theoretical basis for the clinical prevention and treatment of intestinal I/R injury.

肠缺血再灌注（ischemia/reperfusion，I/R）损伤常见于围手术期，死亡率高，机制尚未明确，也无有效防治策略。申请者前期通过代谢组学测序发现菌群代谢产物辣椒素酯在肠I/R后肠道表达相对减少，给予辣椒素酯预处理能够改善肠I/R诱导的菌群失调和肠黏膜屏障损伤。已知菌群失调可诱导巨噬细胞M1型向M2型极化，另外肠巨噬细胞可促使IL-33释放。申请者前期结果发现辣椒素酯可促使IL-33的表达增加，也证实IL-33可以有效改善肠I/R损伤。据此，申请者推测：辣椒素酯通过抑制肠I/R后的菌群失调诱导巨噬细胞M1型向M2型极化、促使IL-33释放从而发挥肠屏障修复作用。本项目拟采用抗生素、粪菌移植实验以及巨噬细胞敲除、IL-33基因敲除小鼠建立肠I/R损伤的在体模型，来研究辣椒素酯在肠I/R损伤中的作用及机制。以菌群代谢产物为治疗靶点，为临床防治肠I/R损伤提供理论依据。

肠缺血再灌注（Ischemia/Reperfusion，I/R）是临床常见急危重症情况，常发生在创伤、休克、严重感染、肠梗阻以及体外循环等临床现象中，其不仅导致肠损伤，还可导致肠外多个器官（肺、脑、心等）损伤，是导致内毒素血症及脓毒症的重要原因之一，具有很高的并发症率和死亡率。肠道菌群与疾病的关系非常密切，是近年的研究热点，但与肠I/R肠损伤的关系尚不明确，本项目就肠I/R肠损伤的发生机制及防治展开了系列研究，现总结如下：1、阐明了肠I/R后肠道菌群及代谢产物的变化特征，发现肠道菌群代谢产物辣椒素酯、普伐他汀能显著改善肠I/R损伤，并揭示了它们的作用机制；2、揭示了肠道菌群是导致肠I/R损伤易感性差异的主要原因，并筛选出差异菌株鼠乳杆菌，证实可通过激活TLR2/myD88信号促进巨噬细胞释放IL-10来减轻肠损伤，率先提出了“肠道菌群及其代谢物在缺血性肠损伤及肠外器官损伤中发挥重要作用”的观点。3、从肠道微生物角度揭示了脓毒症心肌损伤及心功能不全的肠道菌群特征，并发现部分噬菌体及菌株能预测其发生。4、阐明菌群代谢产物丙酸通过GPR41缓解AngⅡ依赖Caveolin-1/ACE2轴而加重的心肌缺血再灌注损伤；5、阐明IL- 10通过抑制Wnt和Notch信号扩大短暂扩充细胞而耗尽Lgr5肠道干细胞。